It is well known in the art of transmission that when a signal encounters a change in the characteristic impedance of a transmission line, a reflected signal is generated. This reflected signal sets up standing waves on the transmission line and depending on the relative location on the line the voltage can be substantially affected. As data transmission speeds increase, the presence of reflected waves can corrupt the integrity of a particular signal. In addition, the presence of standing waves cause a counter electromagnetic force (EMF) to be generated around the transmission line, thus "launching" a wave into free space. In other words, the transmission line becomes an antenna. The launching of a wave is not desirable for data transmission because electromagnetic interference (EMI) is increased and the amount of energy transferred to the receiver is decreased. Because of this and other reasons, it is the general practice in the art of digital transmission to insure that transmission lines are properly terminated thereby providing an uninterrupted characteristic impedance on the transmission line.
In the art of digital transmission, a transmission line may have several transmitters and receivers on the line. If each device (transmitter or receiver) contained a terminating device, the transmission line's impedance would not be properly matched. For this reason a transmission line must only be terminated on the ends, and not in the middle of a chain. In addition, parallel stubs extruding from the chain must not be of any appreciable length.
Prior to the present invention, the installer had to properly determine if physical disposition of the terminating resistors agreed with the theocratical needs.
It is therefore a primary objective to provide an automatic means of detecting the presence of the terminating resistors, and further, to determine if the detected configuration agrees with the expected configuration.